You're saying "romaji" when you mean "romanisation". Yes in Japanese it's called ヘボン式ローマ字, but when people use "romaji" as a loanword in English it's generally understood to mean the written characters, the result of romanisation, not the process of romanisation (and certainly not "Hepburn romanisation specifically as distinct from other romanisation systems", but you've already non-apologised for that).